Certain spinal conditions, including a fracture of a vertebra and a herniated disc, indicate treatment by spinal immobilization. Several methods of spinal joint immobilization are known, including surgical fusion and the attachment of pins and bone plates to the affected vertebras. One known device is a bone interface anchor inserted into at least two spaced-apart vertebras, with a stabilization rod interconnecting the two or more anchors to stabilize the vertebras spanned by the anchors.
During surgical implantation of these prior art stabilization systems, the surgical site is crowded with tissue masses, sponges, and other surgical implements that obstruct access to the anchors. A challenge with current polyaxial screw systems is that lateral connectors typically provide fixation between stabilization rods and a pelvic screw in a spinal construct. However, at the S1-L5 junction, it can be exceedingly difficult or impossible to attach an S1 pedicle screw, L5 pedicle screw, and a lateral connector to a stabilization rod due to special limitations present at the S1-L5 junction. It has been demonstrated that the integrity of the spinal construct is decreased if either the S1 or the L5 pedicle screw is not used. The present invention combines a polyaxial screw body with a lateral connector in a single device that ensures that all necessary fixation points can be achieved in a spinal construct at the S1-L5 junction.
For example, referring to FIG. 5, a portion of a human skeleton illustrates the Sacroiliac region and the L1-L5 and S1 vertebrae. Polyaxial pedicle screws 100 are shown attached to the pedicles of the L2-L4 vertebrae, polyaxial pedicle screws 102 are shown attached to the Sacrum, and polyaxial pedicle screws 104 are shown attached to the Ilium. A conventional polyaxial pedicle screw 106 is attached to one pedicle of the L5 vertebra. Stabilization rods 110a and 110b are illustrated vertically connecting the pedicle screws 100 and 102 on either side of the vertebrae. Ideally, the polyaxial pedicle screw 104 would be attached to the stabilization rod 110a via a lateral connector 112. However, at the S1-L5 junction, the polyaxial pedicle screw 106 may interfere with such connection, as indicated by arrow 114 in FIG. 5, thus making such connection problematic.
Thus, the present invention helps to alleviate a lack of space at the S1-L5 junction as compared to the prior art, allowing the surgeon additional freedom in locating the anchors. The result is a significantly improved polyaxial screw body.